It has been proposed to recover various carboxylic acids from aqueous solutions by direct contact with several different types of polar organic extractants. For example, see the following patents:
______________________________________ Patent Acid Recovered Extractant ______________________________________ U.S. 2,275,862 Acetic C.sub.6 --C.sub.10 dialkyl ketones U.S. 2,395,010 Acetic Amyl acetate or methyl amyl ketone U.S. 2,446,231 Acetic Ethyl disulfide U.S. 2,480,380 Cyanoacetic Methyl isobutyl ketone Czech. 137,177 Formic, acetic Cyclohexanone (C.A. 75: 63155y) or propionic ______________________________________
The organic extractants which have been proposed for recovery of carboxylic acids from aqueous solutions usually are not efficient enough for the processing of highly dilute solutions. In general, such solutions can be recycled or, if they do not also contain more toxic and/or persistent materials, can be discarded without constituting a serious source of pollution. However, this is not always the case. For example, the well-known process for making phenol from chlorobenzene produces a waste brine stream containing about 18-20 wt. % of sodium chloride, about 0.2% sodium acetate and trace amounts of phenol, benzene and acetone. Such streams, which cannot be disposed of in surface waters, also have too high a content of organics to be suitable as a feed to electrolytic chlor/alkali cells. It has now been found that such solutions can be made suitable as cell feeds at a minimal cost. The sodium acetate content of the brine stream is converted to sodium chloride and acetic acid by addition of an equivalent amount of hydrochloric acid. The acetic acid is then suitably removed by the practice of the instant invention.